Apparatus and method for producing metal strip



Dec. 16, 1958 J. B. BRENNAN 2,864,137

APPARATUS AND METHOD FOR PRODUCING METAL STRIP Filed Oct. 25, 1952 5 Sheets-Sheet 1 Dec. 16, 1958 J. B. BRENNAN 2,864,137

APPARATUS AND METHOD FOR PRODUCING METAL STRIP Filed 00%.. 25, 1952 3 Sheets-Sheet 2 117 1a Joyepfz ,5 ,fizgzzzzaa M ffgx Dec. 16, 1958 J. B. BRENNAN 2,864;137

APPARATUS AND METHOD FOR PRODUCING METAL STRIP Filed 001;. 25, 1952v 3 Sheets-Sheet 3 United States Patent APPARATUS AND METHOD FOR PRODUCING METAL STRIP Joseph B.'Brennan, Cleveland, Ohio; Helen E. Brennan, executrix of the estate of said Joseph B. Brennan, deceased Application October 25, 1952, Serial No. 316,873

" .22 Claims. (Cl. 22-57.3)

The present application is a continuation-in-part of my copendin-g application, Serial No. 43,881, now issued as Patent 2,639,490, granted May 26, 1953.

The present application is also a continuation-in-part of my copending application Serial No. 31,690, now issued asPatent 2,648,567.

This invention relates to a machine and method for making metal strip, and more particularly to a machine and method for producing a metal, which is highly reactive" at elevated temperatures, insheet form by the deposition of a layer of overlapping particulate molten particles of said metal. A

* 'It is very difficult to make very thin sheets from billets or sponge briquettes of a metal in a process where high temperatures are involved, particularly where the metal is reactive and where it is important that the sheet of material be free of contamination. This is especially true in the case of highly reactive metals such as titanium.

One of the objects of this invention is to provide a machine forconverting massiveaggregates of metal or metallic alloys into relatively thin continuous sheets of material.

Another object of this invention is to provide a novel machine for making relatively thin tubes of metal.

A further object of this invention is to provide a machine for making metal sheet from molten metal particles and for fusing thesnrfaces of the metal'sheet.

And another object of this invention is to provide a machine wherein high temperatures are used for converting massive aggregates of highly reactive metals into very thin sheets of said metal which are substantially of the same degree of purity as the massive aggregates.

And a further object of this invention is to provide a method for treating particulate metal strip after it has been deposited so as to fuse the surfaces of the strip and so as to densify the strip.

'Still another object of this invention is to provide a method for converting massive aggregates of highly reactive metal or metallic alloys into thin continuous sheets ofsaid metal which are substantially free of contamination or oxidation thereof.

Further objects and advantages of this invention will become apparent as the following description proceeds and the features of novelty which characterize this invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

A preferred embodiment of the invention is shown in the accompanying drawings, in which:

Figure l is a diagrammatic illustration of one form of my invention;

Figure 2 is a-view taken substantially on line 2-2 of Figure l;

Figure 3 is a diagrammatic view of another form of my invention;

Figure 4 is a view taken substantially on line 44 of Figure 3;

Figure '5' is a view taken on line 5-5 ofFigure 3.

Figure 6 is a fragmentary view taken on line 66 of Figure 3; and

Figure 7 is a fragmentary diagrammatic view of a modified form of the invention shown in Figure 1.

Referring now to Figure 1, there is shown a chamber 10 enclosing'a space 12 in which is positioned the apparatus for making sheet metal. The chamber .10 is sealed in a manner so'as to be substantially gas-tight. Bars or billets 14 of metal or metallic alloy project downwardly through openings 16 in the roof of chamber 10 and into space 12. Said opening 16 has a gas-tight seal 18 therein. The lower end of each bar of material 14 is positioned in a cone-shaped, high frequency coil 20, which coil functions in a manner similar to that described in my copending application, Serial No. 31,690, filed June 8, 1948, now issued as Patent 2,648,567. The high frequency coil 20 serves to heat up the metal bar 14 and bring portions of it to a molten stage.

Pressurized gas is then used to atomize the molten metal and to strip particles thereof from the lower ends of bar 14 and deposit them onto a continuously rotating copper drum 22. The means for directing the pressurized gas includes a plurality of conically directed nozzles 24 adjacent each bar 14. Automatic feeding means are provided so that the lowest point15 of bar 14 is maintained substantially in the same location. Said automatic feeding means mayinclude photoelectric means 26 aligned with .point 15 of the bar and responsive to the position of point 15,-in combination with a feeding means 28 responsive to said photoelectric means 26. The heating of bars 14 by the high frequency coils 20 is such that the proper degree of fluidity is maintained at the lower ends of bars 14.

The pressurized gas, directed along the point of the bar 14, is effective to strip particles 30 from the lower end of bar 14. Thereafter, said particles 30 pass through the field of a high frequency coil 32 which maintains the particles molten until they are deposited onto the surface of drum 22. The molten particles are deposited in a layer 34 on the surface of drum 22 at such a rate that a relatively continuous and uniform thickness of metal is deposited on drum 22 as the drum rotates counterclockwise.

The drum 22 is water cooled by means (not shown) in the interior thereof. After particles 30 are deposited as layer 34 on drum 22, the layer 34 passes high frequency coils 36 and 38 which are located 'circumferentially about the drum 22 and spaced closely adjacent layer 34. The high frequency coils 36 and 38 extend over substantially one-half the circumference of the drum 22. These high frequency coils operate at a frequency in excess of 500,000

cycles per second and are operative to fuse the exterior ber 40 and passes through advancing and densifying rollers 42. The rollers 42 serve both to continuously advance the metal strip and also to density the strip by pressing together the particles forming the strip. After the metal strip 34 passes rollers 42, it is carried over a water cooled table 44, while the opposite side of the portion of the strip passing over the water cooled table 44 is subjected to the field of a high frequency coil 46 which fuses the surface of the strip which was adjacent the drum 22.

Thereafter the strip passes through feeding and densifying rollers 43, and thereafter if desired the surfaces of the strip may be additionally fused such as by means of high frequency coils 50. Wherever high frequency coils are used on one side of the metal strip, the opposite side of the metal strip is cooled, and, accordingly, cooling means 52 are provided opposite high frequency coils 50. The metal strip may also be further densified by rollers 54,and thereafter the metalstrip is wound up onaroll56.

While thereis shown the application of high;fre quency energy for the fusing of surfaces of the strip at three separate stations, it .will be understood that the use of such high frequency energy for fusing may be used as often as required and it will also be evident that as many densifying rollers should be used as required. However, it is contemplated that each side of the metal strip be subjected at least once to the high frequency energy field to accomplish fusing of both sides of the metal strip, andthat densifying rollers be provided after fusing takes place. Wherever fusing takes place, that portion of the strip which is being fused on one side thereof should, preferably, also be cooled on the opposite side thereof.

The entire process described above takes place within the space 12 enclosed by chamber and the space 12 is either filled with an inert gas such as argon, or has a substantial vacuum therein, so as to obviate contamination which may occur such as by oxidation. When the process takes place in the presence of an inert gas, and where pressurized inert gas is used to strip the molten particles from the lower ends of bars 14, then means may be provided for recovering the gas, filtering and controlling the temperature of the gas, and for maintaining the pressure in chamber 10 substantially constant. Accordingly, I have shown a pair of suction pumps 58 and 60 which withdraw excess gas from chamber 10 and return it through a filtering and temperature regulating apparatus 61 to a storage tank 62 from whence it is pumped .by pump 64 at a proper pressure through nozzles 24. By proper adjustment of the system, sufficient gas can be withdrawn from chamber 10 so that the pressure in chamber 10 is substantially a fixed amount below the pressure of the gas being discharged through nozzles 24. A pressure or vacuum gage 66 is provided for observing the pressure in chamber 10.

Figure 2 shows the use of a plurality of bars 14 for distributing particulate metal onto drum 22 across the entire width thereof. The nozzles are directed so that the particulate metal is deposited onto drum 22 in a manner to obtain a relative uniform thickness and density of deposit. The nozzle angles are such that the sprays from adjacent billets 14 are caused to overlap for the purpose disclosed in my copending application Serial No. 231,021, now abandoned.

Additional cooling or heating coils may be provided where needed, as for example, the cooling coil 68 which is provided adjacent the portion of the drum upon which there is no deposited particulate metal, so as to cool that portion of the drum prior to its receiving a deposit of particulate metal thereon. The cooling coils 44, 52, and 68, may be connected to a single header 70, as shown diagrammatically in Figure 1.

In Figure 3, there is shown another apparatus suitable for making very thin sheets of particulate metal. In this form of the invention, the finished product is a tube of metal, and the tube is withdrawn continuously from the interior of the chamber in which the tube is formed. In order to form the metal into a sheet formed as a tube, a rotary table or centrifuge 72 is utilized. The rotary table or centrifuge 72 is positioned Within the chamber and is mounted on an axial shaft 74 which passes through thelower wall of the chamber. An electric motor "76 drives shaft 74 and centrifuge 72. The shaft 74 and centrifuge 72 are adapted to be cooled by cooling coils 78 therein which are in communication with a source of cooling fluid (not shown) located outside of the chamber.

The chamber itself is designated generally at 82 and encloses the region above and surrounding the centrifuge. The lower wall of chamber 82 is designated at 83 and is provided with a gas-tight shaft seal 84 surrounding the shaft 74 which passes through wall 83.

Extending throughthe roofof chamber 82 are aplurality of bars of material 85, the lower ends of which are heated by means of heating coils 86. Said bars 85 are distributed inan annular ring located concentrically with the axis Qfthecentrifuge 72. A plurality of high pressure gas nozzles 88 are provided adjacent each bar 85. The highpressure gas directed by nozzles188'atomize and strip particulate metal from the bars 85 and deposit it onto the upper surface of centrifuge 72. As the centrifuge is rotated, the particulate metal 89 which is stripped from the bars 85 and deposited onto centrifuge 72, is thrown outwardly from the surface of centrifuge 72 due to the centrifugal forces thereon.

The particles thrown outwardly by the centrifuge72 are deposited onto previously deposited particles and adhere thereto. Said deposited particles form a tube 93 surrounding the centrifuge 72. The previously deposited particles forming a tube or sheath are being withdrawn continuously axially of the centrifuge and thus a continuous metal tube is formed and withdrawnaxially of the centrifuge. .In order to keep the molten particles in a molten condition as they are being centrifuged, heating coils 90 are provided between centrifuge 72 and the portion of the metal tube upon which the particles are being deposited. The wall portion '92 of the chamber 82, adjacent which the particulate metal is being deposited in the form of tube or sheath 93 is cooled on the outer side thereof by means of a liquidcooled shoe or jacket 94. Thereafter as the tubular metal layer :93 moves axially of the centrifuge 72 it passes adjacent a high frequency coil .96 which serves to fuse the outer surface of the tube 93. Opposite the high frequency coil 96 is a cooling jacket or shoe 98 which cools the inner side of the portion of the tube which is'being fused on the outer side thereof. The tube 93 then passes a high frequency coil 100 which fuses the inner side of the tube as the outer side is cooled by cooling shoe 102. Thereafter, the tube 93 passes between densifying rollers 104 and 106, and 105 and 107, and then passes out from chamber 82 within which the sheet metal making apparatus is positioned. The densifying rollers may also serve as means for continually advancing the tube of metal formed by the apparatus.

As seen in Figure 5, the rollers 104 and 106 only engage and densify peripherally spaced segments of the tube 93. The rollers 105 and 107 are located in a plane spaced parallel to rollers 104 and 106 and are so positioned that they densify the peripherally spaced segments of tube 93 that were not densified by the rollers 104 and 106.

The entire process in Figure 3 is conducted in the presence of an inert gas, or in the presence of a vacuum, and when an inert gas is used, a pump 108 is provided for withdrawing the excess gas from the interior of chamber 82 and for returning it to a storage tank 110 from whence it is pumped by pump 112 through the pressurized gas nozzles 88.

After tube 93 is withdrawn from chamber 82 it may be kept in tubular form or may be cut longitudinally into a plurality of strips. If it is desired to cut the tube 93 into a plurality of strips, a plurality of cutting means may be provided. A typical apparatus for use in cutting the tube 93 into longitudinal strips is shown at 114 in Figures 3 and 6. If desired, the tube 93 may be split with a single slit and thereafter be flattened out into a single wide sheet.

The cuttingmeans 114 comprises a grooved roller 115 and a cooperating knife-edgedroller 116 which is resiliently biased by spring 117 toward roller 115. The rollers 115 are adapted to be supported on the lower wall 83 of the chamber as shown in Figure 3. Adequate means (not shown) are provided for supporting rollers 116 in desired positions. The tube 93 is cut into strips as the tube is drawn past cutting means 114 by means (not shown), such as rollers similar to the densifying rollers. The plurality of cutting means 114 may be spaced apart as desired, to obtain desired widths of metal strip.

Referring again to the densifying rollers, the inner rollers 104 and 105 are journaled on the arms of spiders 118 and 120 which are mounted concentrically on shaft 74. onshaft 74 by means as shown. Adequate means (not shown) are also provided for supporting outer rollers 106 and 107 in desired positions.

Figure 4 illustrates a typical arrangement of metal billets 85'and shows how the plurality of pressurized gas nozzles 88 are connected to headers 122 and 124.

In Figure 7, the modified form shows the use of a hopper 126 of granulated metal substituted for the metal billets 14 in Figure 1. The material in the hopper is fed by gravity through the field ofthe high frequency coils The material in the hopper 126 is fed to the discharge opening thereof at a constant rate by any appropriate means (not shown) such as a constant speed screw, so that the stream of powder discharged from the hopper will produce a substantially constant thickness layer on the drum 22. As the particles pass through the high frequency field they are heated until they become molten, and by that time the particles have reached the surface of the rotating drum 22 where they merge with previously deposited molten particles to form the sheet 34' of particulate metal. Parts in Figure 7, similar to parts in Figure l, are identified with the same numeral as in Figure l with the addition of a prime marking.

Other metals may be processed advantageously according to this invention and other inert gases may be used other than argon. For example, it is also possible to produce nickel carbonyl powder and to aggregate it in porous or densifie'd sheets according to this invention by using CO gas to atomize the nickel.

The process and portions of the machine described herein may be also used advantageously to process bars or billets, castings or briquettes, in such a manner as to produce a progressively densified and fused skin in the article being processed, as the article is being forged or otherwise transformed in shape. The fusing and densifying of the skin is obtained by successive application of high frequency fields to the surfaces of the article so that fusion takes place. The successive and progressive application of high frequency fusion serves to densify the material. What is accomplished broadly by this invention is the production of a uniform porous sheet or bar of material, and thereafter subsequent densifying of it uniformly over spaced areas thereof or in successive sections.

The high frequency heating coils which are used to fuse the outside skin and densify it should be upward of 540,000 cycles in frequency, especially for thin layers, since it is desirable to keep the sections adjacent to the section being fused in a normal and cooled condition. In this invention, it is advantageous to only sectionally fuse the material which it is desired to densify, in order to prevent warpage and distortion. It is desired to use self quenching of the sectionally fused zones as advantageously as possible.

Where desired, the steps of densifying and fusing the deposited particulate metal and the apparatus therefor, may be omitted. The resultantproduct is then a thin porous sheet of metal. If desired, such porous product may later be treated for densifying andfusing in a chamber separate from that in which the sheet is formed, in the manner described herein.

The spiders are restrained from axial movement .therebetween may be vaporized to effect a finer particle spray and/ or to deposit vaporized metal, if desired.

A laminated product of metals of like kind or of different melting points and constituents may be produced by the apparatus disclosed in Figures 1, 3 and 7 by using a previously prepared sheet of material, such as a porous strip of metal formed by the process described hereinabove, as a moving base upon which is deposited additional layers of metal in the presence of a vacuum and/ or in the presence of an inert gas, and then fusing the additional layer of metal to a desired depth as required by the thickness of the additional metal deposited. It is also possible to use other materials as a moving base upon which to deposit and fuse materials involved. Thus, it is also possible to deposit titanium on a quartz fiber base, or paper.

Although I have herein shown and described a preferred embodiment of my invention, manifestly it is capable of modification and rearrangement of parts without departing from the spirit and scope thereof. I do not,

therefore, wish to be understood as limiting this inven-' tion to the precise form herein disclosed, except as I may be so limited by the appended claims.

I claim as my invention:

1. An apparatus for making metal tubing, comprising a molten metal centrifuge for distributing particulate metal circumferentially thereof, means including pressurized inert gas for depositing molten metal particles onto said centrifuge in substantially an annular band substantially concentric with the axis of the centrifuge, a wall surrounding said centrifuge and spaced from the annular band of molten metal particles deposited on said centrifuge and adapted to have the particulate metal deposited thereon to form a sheath, means for moving said sheath axially of said centrifuge, whereby a continuous metal tube is produced, means between the centrifuge and the portion of the sheath upon which the particulate metal is being deposited for heating the centrifuged metal particles, means for fusing the inner and outer surfaces of the metal tube, and means for densifying the material in said metal tube.

2. An apparatus for making metal tubing comprising moving said sheath axially of said centrifuge, whereby acontinuous metal tube is produced, means between the centrifuge and the portion of the sheath upon which the particulate metal is being depositedfor heating the centrifuged metal particles, means for fusing the inner and outer surfaces of the'metal tube, means for densifying the material in said metal tube, and a gas-tight chamber filled with an inert gas enclosing said centrifuge, the portion of said sheath'upon which the particulate metal is deposited, and the means for fusing the inner and outer surfaces of the metal tube.

3. An apparatus for making'metal strip comprising a rotating drum, means for depositing particulate metal onto said rotating drum, whereby a continuous strip of metal is formed thereon, means located adjacent the periphery of said drum for fusing a portion of the outer surface of the metal strip on the periphery of the drum as the drum rotates, and means for cooling the drum.

4. An apparatus for making metal strip comprising a rotating drum, means for depositing particulate metal onto said rotating drum, whereby a continuous strip of metal is formed thereon, means located adjacent the periphery of said drum for fusing, as the drum rotates, a portion of the outer surface of the metal strip on the periphery of the drum, means for cooling the drum, means for stripping the layer of particulate metal from the surface of the drum, means for fusing the inner surface of the strip after it is removed from the drum, and means for densifying the metal strip.

5. An apparatus for making metal strip comprising a rotating drum, means for depositing particulate metal onto said rotating drum, whereby a continuous strip of metal is formed thereon, means for stripping the layer of particulate metal from the surface of the drum, means for successively fusing opposite surfaces of the strip, means alternating with said fusing means for densifying the metal strip, and means for reeling up the metal strip.

6. An apparatus for making metal strip comprising a rotating drum, means for depositing particulate metal onto said rotating drum, whereby a continuous strip of metal is formed thereon, means for strippingthe'layer of particulate metal from the surface'of the drum, and means for simultaneously heating and cooling opposite sides of the strip for fusing the side of the strip being heated.

7. In an apparatus for producing metal in sheet form, means for heating said metal, means including-pressurized inert gas for depositing molten metal particles onto a continuously moving surface, and a gas-tight chamber filled with inert gas enclosing said molten particles of metal and the moving surface upon which the particles are deposited.

8. In an apparatus for producing metal in sheet form, means for heating said metal, means including pressurized inert gas for depositing molten metal particles onto a continuously moving surface, a gas-tight chamber filled with inert gas enclosingsaid molten metal particlesand the moving'surface upon which the particles are deposited, and means for maintaining'the pressure in-said chamber substantially constant and below the pressure of said pressurized gas.

9. In an apparatus for producing metal in sheet form, means for heating the metal, means-including pressurized inert gas for depositing molten metal particles onto a -continuously moving surface, a gas-tight chamber filled with inert gas enclosing said molten particles and the moving surface upon which the particles are deposited, means-for maintaining the pressure in said chamber substantially constant and below the pressure of said pressurized gas, and means within said chamber for fusing the surfaces of the metal sheet.

10. A method for forming a continuous metal strip comprising the Steps of depositing molten metal particles onto a moving surface in overlapping relation with previously deposited particles, fusing one surface of the strip formed on said continuously moving surface while simultaneously cooling the other surface of said strip, and then stripping the metal strip from said continuously moving surface.

11. A method for forming a continuous metal strip comprising the steps of depositing molten metal particles onto a moving surface in overlapping relation with previously deposited particles, fusing one surface of the strip formed on said continuously moving surface While simultaneously cooling the other side of said strip, then stripping the metal strip from said continuously moving surface, then fusing the particles on the opposite side of the metal strip, and then densifying the strip by pressing the particles together. 7

12. A method for forming a continuous metal strip comprising the steps of depositing molten metal particles onto a moving surface in overlapping relation with previously deposited particles, then successively fusing each surface of the metal strip to fuse the particles on said surface While simultaneously cooling the opposite surface, and pressing the particles together to densify the metal strip.

l3. A method for forming continuous metal sheets from metal billets comprising the steps of blowing molten metal particles off the ends of heated metal billets, de-

8 positing said molten metal particles onto a moving surface in overlapping relation with previously deposited particles, and then successively fusing each side of the total sheet so formed While simultaneously cooling the opposite side of the metal sheet.

14. Adevice for making a metal strip comprising means defining an air-exhausted chamber, means for depositing particulate metal in layer form in said chamber, guiding means for guiding the layer so formed from the depositing means and along a predetermined path, means for advancing said layer of .particulate metal along said predetermined path, and heating means positioned along both sides of the path along which said particulate metal layer is advanced for separately fusing both sides of the layer so deposited to bond each side of the particulate metal'layer.

15. A device for making a metal strip comprising means defining an air-exhausted chamber, means for depositing particulate metal in layer form in said chamber, guiding means for guiding the layer so formed from the depositing means and along a predetermined path, means for advancing said layer of particulate metal along said predetermined path, and heating means positioned along bothsidesof the path along Which saidparticulate metal layer is advanced-for separatelyfusing both sides of the layerso deposited to bond each side of theparticulate metal layer, said heating means for the sides of the metal layer being spaced longitudinally along said path of advance of said layer of metal, so that: the opposite sides of said layer arefused in succession.

l6. A device for making a metal strip comprising means definingan air-exhausted chamber, means for depositing particulate metal in layer form in said chamber, guiding means for guiding the layer so formed from the depositing means and alon g a predetermined path, means for advancingsaid layer of particulate metal along saidpredetermined path, heating means positioned along both sides of the path along which said particulate metal layer is advancedfor separately fusing both sides of the layer so deposited to bond each side of the .particulate metal layer, said heating means for the sides of the metal layer being spaced longitudinally along said path of advance of said layer of metal, so that the opposite sides of said layer arefused in succession, and cooling means positioned along the path of advance of said metal layer and positioned opposite said heating means to provide for simultaneously cooling each side of said metal layer as the other side of said layer is being fused.

17. A device for making a metal strip comprising means defining'an air-exhausted chamber, means for depositing particulate metal in layer form in said chamber, guiding means for guiding the layer so formed from the depositing means and along a predetermined path, means for advancing said layer of particulate metal along said predetermined path, heating means positioned along both sides of the path along which said particulate metal layer is advanced for separately fusing both sides of the layer so deposited to bond each side of the particulate metal layer, and means positioned along said path of advance and positioned to engage opposite sides of said metal layer to densify same after the sides of said layer have been fused.

18. A method of producing continuously a relatively thin strip of metal comprising the steps of continuously feeding a supply of relatively thick metal stock, as it is being consumed, into an air-exhausted space, heating said metal stock in said air-exhaustedspace to melt same, depositing the melted metal in particulate form in a thin continuous layer onto a backing which is continuously advanced from the region Where metal is being deposited along a predetermined path, and successively fusing opposite sides of said layer of particulate metal.

19. A method of producing continuously a relatively thin strip of metal comprising the steps of continuously feeding a supply of relatively thick metal stock, as it is being consumed, into an air-exhausted space, heating said metal stock in said air-exhausted space to melt same, depositing the melted metal in particulate form in a thin continuous layer onto a backing which is continuously advanced from the region where metal is being deposited along a predetermined path, successively fusing opposite sides of said layer of particulate metal, and densifying said layer of particulate metal after same has been fused.

20. An apparatus for making metal tubing, comprising a molten metal centrifuge for distributing particulate metal circumferentially thereof, means for depositing molten metal particles onto said centrifuge in substantially an annular band substantially concentric with the axis of the centrifuge, a wall surrounding said centrifuge and spaced from the annular band of molten metal particles deposited on said centrifuge and adapted to have the particulate metal deposited thereon to form a sheath, means for moving said sheath axially of said centrifuge, whereby a continuous metal tube is produced, and means between the centrifuge and the portion of the sheath upon which the particulate metal is being deposited for heating the centrifuged metal particles.

21. An apparatus for making metal tubing, comprising a molten metal centrifuge for distributing particulate metal circumferentially thereof, means for depositing molten metal particles onto said centrifuge in substantially an annular band substantially concentric with the axis of the centrifuge, a wall surrounding said centrifuge and spaced from an annular band of molten metal particles deposited on said centrifuge and adapted to have the particulate metal deposited thereon to form a sheath, means for moving said sheath axially of said centrifuge, whereby a continuous metal tube is produced, and means for fusing the inner and outer surfaces of the metal tube.

22. An apparatus for making metal tubing comprising a molten metal centrifuge for distributing particulate metal circumferentially thereof, means for depositing 10 molten metal particles onto said centrifuge in substantially an annular band substantially concentric with the axis of the centrifuge, a wall surrounding said centrifuge and spaced from the annular band of molten metal particles deposited on said centrifuge and adapted to have the particulate metal deposited thereon to form a sheath, means for moving said sheath axially of said centrifuge, whereby a continuous metal tube is produced, means for fusing the inner and outer surfaces of the metal tube, and means for densifying the material in said metal tube.

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